Re: [RFC PATCH] fs: allow opening overlayfs/erofs layers through O_ALT

On Sun, 19 Jul 2026 at 16:13, Andy Lutomirski [off-list ref] wrote:

This gives me the willies a bit.  It's very cool, but it has some
potential security issues that I think we need to watch out for.  As
sort-of prior art, NTFS supports alternate streams and Reiser4, ahem,
supported files-as-directories.

I realized that we can keep the creepiness factor minimal by
introducing this first in procfs only.   That way zero changes are
needed in the path lookup code:

sprintf(buf, "/proc/self/fd-alt/%d/%s", base_fd, alt_path);
alt_fd = open(buf, O_PATH);

Thanks,
Miklos